Re: Avoid VPATH-related distcheck failures with non-GNU make

[Ralf Wildenhues]

Hello Stefano,

* Stefano Lattarini wrote on Sat, Jan 15, 2011 at 04:50:31PM CET:
> On Saturday 15 January 2011, Ralf Wildenhues wrote:
> > ensure_distcheck_ ()
> > {
> >   if $MAKE --version -v | grep GNU; then
> >     $MAKE distcheck
> >   else
> >     :
> >   fi
> > }

> Hmm... To me, this sounds an awful lot like sweeping the dirt under
> the rug.

OK, so here's a more open alternative: let's try to fix the failures.
Are you going to work on this, or at least provide significant help?
The current amount of failures from this hunting for regressions in
Automake proper harder than it should be, because there are many
failures which could be testsuite regressions, or regressions for
features we don't advertise, or long-standing issues for which it thus
is not imperative that we fix them quickly.

I reject the notion of disallowing VPATH builds with GNU make only.
The reason is simple: I make good use of this feature every time I test
the Automake package with some non-GNU make (I build several platforms
off of one tree shared via NFS).  It would make my testing significantly
harder if GNU make needed to be added to the mix.

Just diagnosing non-GNU make at configure time in a VPATH setup is
slightly problematic because many people still do
  ../configure
  gmake

(note the missing MAKE=gmake on the configure command line).  Or, as I
also happen to do, go back to a build tree several months old and do
'git pull && cd build && make' in it, forgetting that MAKE=gmake was set
at configure time (portably warning about this at make time is
surprisingly hard to do right, when you can't assume GNU make).

> What about a more radical but IMHO more honest approach, to be implemented
> in four steps:
> 
>   [1] Clearly document in the manual that VPATH builds are expected to
>       work with GNU make only.

See above.  For lots of packages, portable make works just fine even in
VPATH mode.  I'm fine with mentioning that GNU make or non-VPATH should
be tried if there are problems with another make in a VPATH build.

>   [2] Update AM_INIT_AUTOMAKE to make it complain(*) if it detects that
>       $MAKE is not GNU make but a VPATH build is being attempted.  The
>       user should be allowed to override this check, obviously.

See above.

> (*) With a warning or an error?  Not sure yet, but it should be warning
>     in the next Automake version, not to suddenly disrupt backward
>     compatibility.

Generally, I want to keep even git master of Automake always in a
close-to-releasable state.  Even if all current failures are only
issues in the testsuite, or long-standing bugs, this is too much to
just ignore it.

Cheers,
Ralf